Fiber optics are long, thin strands of very pure glass or other materials about the diameter of a human hair used to transmit light. Each strand of optical fiber generally has three components, a core, cladding, and a buffer coating or jacket. The core is a thin glass center of the fiber where the light travels. The cladding is the outer optical material surrounding the core that reflects the light back into the core. The buffer coating is a plastic coating that protects the fiber from damage and moisture. Generally, fiber optic strands can be arranged in bundles called optical cables and used to transmit light signals over long distances.
Fiber optic communication channels are widely used in communication systems around the world. When constructing, maintaining, or repairing a fiber optic network, one or more fibers may need to be connected to other fibers in a communication link. Such interconnections are a critical part of the fiber optic communication system. To mate two or more fibers, optical connectors or “splices” are used. These are devices that place the ends of a transmitting and receiving fiber in aligned proximity so the light from one fiber is inserted into the other fiber.
Connections in a fiber optic system should have low insertion loss. Insertion loss occurs when the optical energy from one fiber is not properly inserted into the receiving fiber, and can result from such things as variations in fibers, misalignment of the fibers, and optical aberrations and irregularities at the ends of the sending and receiving fibers. An ideal interconnection between fibers would require two fibers that are optically and physically identical to one another, without aberrations, held by a connector that perfectly aligns the two fiber cores. Of course, no perfect connector exists, and limitations on their effectiveness are imposed by such considerations as variations in the fibers themselves, tolerances of the connectors or splices, cost of production, and ease of use.
FIGS. 1A-1C show, respectively, three types of fiber-related sources of loss. In FIG. 1A, the core of the fiber is shown offset, which means the cladding is thicker on one side than the other. This misalignment of the core can cause insertion loss, as the fiber to which this example may be joined would probably not have an identical misaligned core. The misalignments between the sending and receiving core allow light to impinge on the cladding instead of the core, causing insertion loss.
FIG. 1B shows an example where the two cores are properly aligned, but are not of the same shape. In this example, the transmitting core does not fully overlap the receiving core. Light in the transmitting core thus impinges on the receiving fiber outside its core, and this results in loss.
FIG. 1C shows another source of loss. In this example, the numerical apertures of the cores are different between the transmitting fiber and the receiving fiber. Thus, the cone of light from a transmitting fiber will extend beyond the core of the receiving fiber, allowing light to escape. Numerical aperture issues are often solved by the addition of microlenses attached to the ends of a fiber or positioned near the end of the fiber to capture the light emitted and focus it on an area within the core of a receiving fiber. However, fabricating and positioning microlenses can be a time consuming and expensive process.
FIGS. 2A-2C show, respectively, three types of mechanically caused loss. FIG. 1A shows a situation in which the two fibers are properly aligned along their axes, but there is a gap between the two fibers. This can cause loss as the diverging light from the transmitting fiber expands to impinge on an area greater than the core of the receiving fiber. The farther the two fiber cores are apart, the greater likelihood of loss.
FIG. 2B shows a situation in which the two fibers are parallel with one another, but are laterally offset. In this case, light emitted from one fiber will only partially transition into the core of the receiving fiber, resulting in loss.
FIG. 2C shows an example of angular misalignment. In this example, the two fiber cores are properly aligned, except that the receiving fiber is set at an angle with respect to the transmitting fiber. Again, this causes some loss as not all the light from the transmitting fiber transitions into the core of the receiving fiber.
These and other insertion loss problems have been addressed, for example, by the addition of microlenses on the ends of fibers. FIG. 3 shows how microlenses work. In this example, the lens from the transmitting fiber captures light from the transmitting fiber and focuses it onto the region of the receiving fiber. In this example, another microlens attached to the end of the receiving fiber captures the light and focuses it onto the core of the receiving fiber. Though microlenses are capable of reducing loss in fiber optic connections, they are difficult to fabricate and properly align and attach to fiber ends. Further, microlenses cannot fully solve the problems, as aberrations on the ends of, for example, a poorly cleaved fiber, may cause light to diverge even outside the width of the lens.
These and other problems with fiber connections are exacerbated when multiple fibers are to be connected in a single interconnect comprising a plurality of fibers. FIG. 4 shows an example of a typical interconnect 400. A ribbon cable 406 of a plurality of fibers aligned side by side (in this example) enters the rear of the interconnect 400. Individual fibers 402 are shown on the connection (front) side of the interconnect 400. In this example, the fibers 402 are shown aligned in a row. Alignment devices 404 are also shown.
Because of the small size of optical fibers, the tolerance in connection technology must be very tight. Materials like plastics may not hold a tolerance and cause misalignment of the fibers. This problem is increased by the fiber related and mechanical related issues described above. Therefore, there is a need in the art for a cheap, efficient way to couple ribbons or cables of fiber optics together.
Arrayed Multi-Fiber Connector
In one embodiment, the present innovations include a plurality of fiber optic channels or fibers aligned in, for example, an array structure (e.g., a two-dimensional array), and inserted into a connector apparatus, either fully or partly assembled. A non-mechanical segmentation process is used to segment the fibers, preferably after assembly into the array.
In preferred embodiments, the non-mechanical segmentation process includes using heat energy (such as that of an IR wavelength laser) to segment the fibers. Preferred processes include the formation of hemispherical integrated lenses from the ends of the fibers. In preferred embodiments, the fibers are placed in either a partly assembled or fully assembled connector apparatus such that the fibers form the array structure, and the ends of the fibers are segmented using the aforementioned process. This leaves the optical fibers with lenses and minimizes the alignment tolerances and the need for adding discrete lenses. Because the fiber ends are also integrated, there are fewer mechanical parts to align which decreases issues in field applications. In preferred embodiments, the array is sealed, e.g., hermetically sealed, to protect it from the elements and other dangers during use.
These and other aspects of the present innovations are described more fully below.